Catálogo de publicaciones - revistas

<jats:p>Most of the universe is dark matter, but the actual nature of this matter is unknown. Gravitational lensing—the bending of light from distant stars by matter—may offer some clues. As Hewett and Warren discuss in their Perspective, recent observations of gravitational microlensing by compact masses are leading to a better understanding of how the universe is populated by matter in our own galaxy and elsewhere.</jats:p>

<jats:p>Finding a phone number in a directory when one knows the name is easy; much harder is finding the name given the number. On average, a search algorithm will have to scan half the total number of entries. If the database or directory is extremely large, the search may be impossible with classical computers. New possibilities emerge, however, with quantum computing. As Brassard discusses in his Perspective, a new algorithm developed by L. K. Grover enables much faster searching of large databases if one uses a quantum computer.</jats:p>

<jats:p> Many growth factors exert their effects on cells by simulating intracellular kinases, which add phosphate groups to proteins. Two reports on <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="661" related-article-type="in-this-issue" vol="275" xlink:href="10.1126/science.275.5300.661" xlink:type="simple">p. 661</jats:related-article> and <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="665" related-article-type="in-this-issue" vol="275" xlink:href="10.1126/science.275.5300.665" xlink:type="simple">p. 665</jats:related-article> of this week's issue implicate the oncogenic kinase Akt in IGF-1-mediated neuronal survival (Dudek <jats:italic>et al</jats:italic> .) and show how lipids can regulate the activity of Akt (Franke <jats:italic>et al</jats:italic> .). In his Perspective, Hemmings discusses these results and several other recent reports about Akt and its unique mode of activation by phospholipids. </jats:p>

<jats:p>What causes Alzheimer's disease? Selkoe's Perspective reviews recent research identifying four different genetic causes of Alzheimer's disease and suggests that all four point toward the deposition of amyloid beta in the brain as the initial trigger for the disease.</jats:p>

<jats:p>When cells divide, the chromosomes must be delivered flawlessly to the daughter cells. Missing or extra chromosomes can result in birth defects and cancer. Chance events are the starting point for chromosome delivery, which makes the process prone to error. Errors are avoided by diverse uses of mechanical tension from mitotic forces. Tension stabilizes the proper chromosome configuration, controls a cell cycle checkpoint, and changes chromosome chemistry.</jats:p>